1. Field of the Invention
In recent years, various game apparatuses in which characters are displayed in a simulated 3D space generated on a monitor screen have been spread. Some of such game apparatuses are known to simulate skiing, motor-booting, snow boarding, skate boarding, car race, bicycle race, etc. These sports are generally played outdoors, and weather changes such as rainfall and snowfall are presented as presentation effects conforming to actual sports in these video games.
2. Description of the Related Art
For example, in a sport relay broadcast such as a bicycle race, raindrops (water drops) may be attached to a lens of a camera during the rainfall. Even in the video games simulating the above sports, such a presentation as if water drops were attached to the camera lens catching game characters is made to give game players the better feeling of being present.
Conventionally, the water drops attached to the camera lens have been expressed by the following method. Specifically, a 3D model as a background image is rendered, and white round models having a reduced transparency are additionally rendered. A background image and water-drop images are combined in this way, thereby realizing such an expression as if water drops were attached to the camera lens.
FIG. 7 is a diagram showing an example of a conventional game scene expressing a water drop attached to a camera. A game scene 700 shown in FIG. 7 is a game scene in which a viewpoint of a camera is set in front of a bridge. On this game scene 700 are displayed a background image 703 comprised of 3D models of piers 701 and a girder 702, and a water-drop image 704. The pier 701, the girder 702, etc. are not displayed in this water-drop image 704 as shown in FIG. 7, and a water drop attached to the camera lens is expressed by blurring or shading the water-drop image 704 into white.
However, in the case that a water drop is actually attached to the camera lens, not only a landscape within a range of the water drop, but also a landscape within a range larger than the range of the water drop can be seen through the water drop in a distorted manner because light is refracted due to a difference in the refractive index between the water drop and the lens and according to a 3D shape of the water drop. On the other hand, an image portion of the water drop is only displayed while being blurred or shaded into white according to the conventional method, and no such display is made to let the landscape within the range wider than the range of the water drop seen through the water drop. Users find such a display lack reality.
It is possible to reflect the refracted background image on the 3D model of the water drop by simulating the refraction of light in view of the refractive indices of the water drop and the lens and the shape of the 3D model of the water drop. Such a processing is very complicated, and it is difficult to use such a processing for the presentation of the video game in view of a processing ability of the video game apparatus.